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Probability: Sample Proportions and Surveys

Approximately 5% of U.S. families have a net worth in excess of $1 million and thus can be called millionaires. However, a survey in the year 2000 found that 30% of Microsoft's 31,000 employees were millionaires. If random samples of 100 Microsoft employees had taken that year, what's the probability that the sample proportion of millionaires will fall between 0.25 and 0.35??

A. 0.1379
B. 0.2758
C. 0.7242
D. 1.0911

Solution Preview

The correct answer is C.

In order to answer this, we need to find the distribution of the sample proportion. We know that the mean of the sample proportion will be equal to the population proportion, in this case, 0.30. The standard deviation of a sample proportion can be calculated as:

sqrt ( p*(1-p)/n )
[sqrt() means ...

Solution Summary

This solution provides equations and explanations for solving a probability question involving sample proportions.